The rapper -- whose real name was Timothy J. Parker -- died last Friday ... according to the hip-hop collective Quannum Projects, which first told Rolling Stone. "Tim peacefully departed this earth to be with our ancestors on Friday, June 18, 2021."

The statement from the collective added, "He is survived by two brothers, one sister, many nieces and nephews, countless friends, and fans across the globe. We ask that the family's privacy is respected as we mourn the tremendous loss of our dear brother."

Gab had battled kidney failure in 2014 caused by type 1 diabetes ... forcing him to undergo dialysis several times a week. He reportedly got a kidney transplant in January 2020.

Xavier "Chief Xcel" Mosley -- Gab's partner and co-founder of the Bay Area group -- said, "Our brother was an MC's MC who dedicated his life to his craft. One of the greatest to ever do it. He's the most prolific person I've ever known."

He added, "He was all about pushing the boundaries of his art form in the most authentic way possible. He truly believed in the healing power of music. He viewed himself as a vessel used by a higher power whose purpose was to give positive contributions to humanity through Rhyme."

Xcel and Gab teamed up while studying at the University of California Davis. They released several EPs in the mid-90s but it was their 1999 full-length album "Nia" that brought them critical acclaim.

That same album included their iconic hit "Alphabet Aerobics" ... with Gab taking the spotlight thanks to his linguistic mastery of the alphabet with deft speed.

Daniel Radcliffe was a fan of the group ... and proved it with one helluva performance of 'Alphabet' in 2015 as a guest on "The Tonight Show Starring Jimmy Fallon."

It was so well received ... Gab himself reportedly said Daniel "killed it." He went on to release 3 solo albums. He reportedly has almost 100 tracks for future releases.

Gift of Gab was 50.